Project Summary In the US 40,000 people are diagnosed with idiopathic pulmonary fibrosis (IPF) every year. Diagnosis of IPF is essentially a death sentence since patient survival is only 2-3 years after diagnosis. Recent advances in understanding IPF have led to the development of two new drugs to treat IPF, nintedanib and pirfenidone, however neither drug significantly increases life span after diagnosis. Our research has been focused on understanding the role or oxidative stress in the onset and progression of IPF. Cellular oxidative stress has long been linked with IPF, however past treatments with antioxidant compounds have proven ineffective. We believe that these past therapies have failed because there is a lack of understanding of the mechanisms involved in oxidative stress at a subcellular level. Through our research, we will gain insight into the underlying mechanisms and signals associated with cellular oxidative stress in the endoplasmic reticulum (ER). The ER is where a clear majority of proteins are properly folded, and any changes in the redox status of the ER will have a large impact on the redox state of many proteins. The new knowledge gained will allow for the development of targeted antioxidant therapies to treat IPF. We hypothesize that by alleviating oxidative stress in lung epithelial cells we can halt epithelial cell death and thus stop and reverse the progression of IPF. To test our hypothesis, we will treat lung epithelial cells with a pro-apoptotic signaling protein, Fas ligand (FasL), and measure levels of a key cellular oxidant, hydrogen peroxide (H2O2), in the ER. We will then assess the effects of modulating the activity of the most highly expressed ER H2O2 scavenger, peroxiredoxin 4 (Prdx4), on ER redox homeostasis and cell death. To further verify our findings, we will conduct studies using a mouse model of pulmonary fibrosis where we can induce the ablation of, Prdx4. Using this model, we will show the effects of decreasing cellular hydrogen peroxide levels on the development and progression of pulmonary fibrosis. Finally, we will verify that our findings are relevant to human IPF by conducting a similar set of experiments to access hydrogen peroxide levels and protein oxidation states in human IPF lung tissue. Upon completion of our research we will have a better grasp on the role of oxidative stress in the ER, which can be utilized to create more targeted antioxidant therapies for treatment of IPF.